1. Technical Field
The present invention relates to a liquid discharging apparatus, a head unit, an integrated circuit device for capacitive load driving, and a capacitive load driving circuit.
2. Related Art
In a liquid discharging apparatus, such as an ink jet printer, which discharges ink and prints an image or a document, an apparatus which uses a piezoelectric element (for example, a piezo element) is known. The piezoelectric elements are provided corresponding to each of a plurality of nozzles in a head unit, and each of the piezoelectric elements is driven in accordance with driving signals. Accordingly, a predetermined amount of ink (liquid) is discharged from the nozzle at a predetermined timing, and a dot is formed. Since the piezoelectric element is a capacitive load, such as a capacitor, in terms of electricity, it is necessary to supply sufficient amount of current in order to operate the piezoelectric elements of each nozzle.
For this reason, in the above-described liquid discharging apparatus, the piezoelectric elements are driven as a driving signal which is amplified by an amplifying circuit is supplied to a head unit (ink jet head). An example of the amplifying circuit includes a type which performs current amplification with respect to a source signal before the amplification by using a class-AB amplifier, but since energy efficiency is not excellent, in recent years, a type in which a class-D amplifier is used has been suggested (refer to JP-A-2010-114711).
In order to obtain the discharge accuracy by a class-D amplifier for an ink jet head (achieve high accuracy of an output waveform), high oscillation frequency (1 MHz to 8 MHz) which is 20 or more times higher than that of an audio class-D amplifier is necessary. However, due to the high oscillation frequency, the influence of various types of noise is likely to occur. For this reason, the inventors have found that, in the class-D amplifier for ink jet, a component layout of an IC is less significant, but is considered important in the audio class-D amplifier for reducing the noise. In addition, for example, there is a risk of malfunction of a temperature detection circuit which performs a thermal shutdown function due to also being influenced by noise.